1. Field of the Invention
The present invention relates to a shaft composite structure between a turbine rotor made of ceramic and a compressor impeller made of metal material.
2. Related Art Statement
Referring to FIG. 2, such a turbine rotor has a construction such that a shaft 22 integrally formed with a turbine rotor 21 is fixed to a metal sleeve 24 integrally formed with a rotary shaft 23 made of metal material by means of known connection methods such as a pressure insertion, thermal insertion, chill insertion, soldering and the like.
In the turbine rotor having the construction mentioned above, the stress concentration is liable to occur at a connection edge 25 between the ceramic shaft 22 and the meal sleeve 24, so that the ceramic shaft 22 is liable to be broken from the connection edge 25.
Moreover, when the ceramic turbine rotor rotates at a high speed, the ceramic shaft 22 is also liable to be broken from the connection edge 25 due to a bending moment produced from a slight unbalance of weight distribution.